An apparatus and method for protecting an AC load from half-wave rectified power detects a half-wave rectified voltage or current, sets a status indication indicating the type of asymmetric fault causing the half-wave rectified power, and selectively turns the SSPC ON or OFF depending on the type of fault. There are two example circumstances that can cause an asymmetric fault: when the SSPC is OFF and a switch is shorted (“SSPC Failed Shorted”), or when the SSPC is commanded ON and a switch remains open (“SSPC Failed Open”). If the SSPC is OFF when the half-wave rectified AC voltage or current is detected, an “SSPC Failed Shorted” status indication is set, and the SSPC is turned ON to clear the fault. If the SSPC is commanded ON when the half-wave rectified AC voltage or current is detected, an “SSPC Failed Open” status indication is set, and the SSPC is turned OFF to clear the fault.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A solid state power controller comprising: at least one first switch; at least one second switch; and a controller, wherein the controller is operable to detect an asymmetric fault condition, wherein the controller is operable to either open or close the at least one first switch and the at least one second switch in response to the asymmetric fault condition, and wherein when the controller detects a shorted switch when the solid state power controller is OFF, the controller will turn the solid state power controller ON.
2. The solid state power controller of claim 1 , wherein the at least one first switch is oriented to have an intrinsic body diode that is reverse-biased, and wherein the at least one first switch is coupled to an input voltage line, and the at least one second switch is oriented to have an intrinsic body diode that is forward-biased, and wherein the second switch is coupled to a load output.
3. The solid state power controller of claim 2 , further including a current sense resistor.
4. The solid state power controller of claim 3 , further including a signal conditioning and logic module, wherein the signal conditioning and logic module is operable to obtain current and voltage measurement data, and to send the measurement data to the controller.
5. The solid state power controller of claim 4 , further including a gate drive coupled to the at least one first switch and the at least one second switch, wherein the gate drive is operable to receive commands from the controller to open or close the at least one first switch and the at least one second switch.
6. The solid state power controller of claim 1 , further comprising: a plurality of first switches, wherein the plurality of first switches are in parallel; and a plurality of second switches, wherein the plurality of second switches are in parallel, and wherein there are an equal number of first and second switches.
7. The solid state power controller of claim 1 , wherein the at least one first switch and at least one second switch are MOSFETs.
8. The solid state power controller of claim 1 , wherein said controller detects an asymmetric fault condition by measuring an output voltage at an output of the solid state power controller, measuring an input voltage at an input of the solid state power controller, determining a voltage drop across the solid state power controller based on the input voltage and the output voltage, and detecting an asymmetric fault only when said determined voltage drop exceeds a threshold.
9. The solid state power controller of claim 1 , wherein said controller detects an asymmetric fault condition by measuring a voltage at an output voltage of the solid state power controller, and detecting an asymmetric fault only when the output voltage is greater than or equal to a threshold.
10. The solid state power controller of claim 1 , wherein said controller detects an asymmetric fault condition when a difference in alternate half cycles of voltage of the solid state power controller is greater than or equal to a threshold value.
11. The solid state power controller of claim 1 , wherein said controller detects an asymmetric fault condition when a difference in alternate half cycles of current of the solid state power controller is greater than or equal to a threshold value.
12. A solid state power controller comprising: at least one first switch; at least one second switch; and a controller, wherein the controller is operable to detect an asymmetric fault condition, and wherein the controller is operable to either open or close the at least one first switch and the at least one second switch in response to the asymmetric, fault condition; and wherein an ON state of the solid state power controller corresponds to the at least one first switch and the at least one second switch being closed, and an OFF state of the solid state power controller corresponds to the at least one first switch and the at least one second switch being open, and wherein if the controller detects a shorted switch when the solid state power controller is OFF, the controller will turn the solid state power controller ON.
13. The solid state power controller of claim 12 , wherein if the controller detects that a switch remains open when the solid state power controller is commanded ON, the controller will turn the solid state power controller OFF.
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December 26, 2006
February 2, 2010
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